<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<script type="text/javascript">
			var a=100; /* 在js中用var关键字声明一个变量*/
			document.write(b);
			var age=20;
			document.write(age);
		</script>
	</head>
	<body>
		
	</body>
</html>